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The data showed that 36 per cent of asylum applications in between 2004 and 2014 were from migrants "encountered by local immigration and enforcement staff.

Figures released by Home Office minister Lord Bates in reply to a question tabled by crossbench peer Lord Green of Deddington showed such migrants accounted for 83,912 of the 231,100 asylum applications received by the Home Office over the 10-year period.

Tory MP Philip Hollobone said: "This is yet further extraordinary evidence of the extent to which our immigration system is being abused by people falsely claiming asylum.

"These people are effectively claiming to be refugees but they are only doing this to try and continue their illegal stay in the country.

"It needs to be remembered that these people make it more difficult for genuine asylum seekers to get the help they need because they clog up the system with their false claims."

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Many asylum seekers are thought to be economic migrants

Alp Mehmet, deputy chairman of the pressure group Migration Watch founded by Lord Green, said: "What these figures show is that having arrived, then by hook or crook, these people will seek any possible means to stay.

This is yet further extraordinary evidence of the extent to which our immigration system is being abused

Tory MP Philip Hollobone

"These figures suggest that many of those claiming asylum are in fact economic migrants."

Former Labour minister Keith Vaz, chairman of the Commons Home Affairs Committee, said: "It is deeply concerning that a third of all asylum applications have been made by illegal migrants and over-stayers.

"The very principle of seeking asylum is that you feel persecuted at the time you arrive, not saying you feel persecuted after arriving illegally or for different reasons and then remaining in the country until you are apprehended.

"This is a significant clog in the immigration system, and we should ensure that this is not to the detriment of vulnerable people with a legitimate claim of asylum.

"It is one thing for the Government to say it's tough on illegal immigration - it's another to actually take control of issues like these."

Home Office statistics also concerned that many migrants who claimed asylum after overstaying their visa period still had a good chance of having their application granted.

About 19,200 applicants who had overstayed were subsequently given asylum status or permitted to remain in the UK for other reasons.

Home Office figures showed that 31 per cent of asylum seekers who underwent “enforced removal" from the UK last year (2015) had been over-stayers while 44 per cent were illegal entrants.

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The number of cases waiting for a decision has more than doubled between 2010 and 2015

Separate figures for last year showed that 70 per cent of asylum seekers removed from the UK had made their applications after being identified as illegal immigrants

or over-stayers. The total was up from 58 per cent in 2009.

Yesterday's figures are expected to intensify pressure on Prime Minister Theresa May and Home Secretary Amber Rudd to curb abuse of the asylum system.

At last year's Tory conference, Mrs May said she wanted to work with European leaders and the United Nations to review the international definitions of asylum and refugee status.

She said the move was necessary because there was a "huge difference" between a young family fleeing violence and "a student who claims asylum once he has been discovered overstaying his visa, or a foreign criminal about to be sent to prison in his own country".

A Home Office spokesman said: “Every claim for asylum I the UK is carefully considered on its own merits.

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Asylum application are now the highest they have been for a decade

“We expect anyone found not to need our protection or anyone who has no legal right to remain in the UK, to leave the country.

“If they do not leave voluntarily, immigration enforcement staff will seek to enforce their departure."

Asylum applications in the UK have risen to their highest level in a decade following the European migration crisis.

Overall, the number of cases waiting for a decision has more than doubled between 2010 and 2015 from 11,000 to 26,000.

Rob Whiteman, former head of the UK Border Agency, admitted last month that ministers did not have the “resources or political levers to deport hundreds of thousands of people".